Synthesis and in vitro antibacterial, antifungal, anti-proliferative activities of novel adamantane-containing thiazole compounds

A series of (Z)-N-(adamantan-1-yl)-3,4-diarylthiazol-2(3H)-imines (5a-r) was synthesized via condensation of 1-(adamantan-1-yl)-3-arylthioureas (3a-c) with various aryl bromomethyl ketones (4a-f). The structures of the synthesized compounds were characterized by 1H NMR, 13C NMR and by X-ray crystallography. The in vitro inhibitory activities of the synthesized compounds were assessed against a panel of Gram-positive and Gram-negative bacteria, and pathogenic fungi. Compounds 5c, 5g, 5l, 5m, and 5q displayed potent broad-spectrum antibacterial activity, while compounds 5a and 5o showed activity against the tested Gram-positive bacteria. Compounds 5b, 5l and 5q displayed potent antifungal activity against Candida albicans. In addition, the synthesized compounds were evaluated for anti-proliferative activity towards five human tumor cell lines. The optimal anti-proliferative activity was attained by compounds 5e and 5k which showed potent inhibitory activity against all the tested cell lines. Molecular docking analysis reveals that compounds 5e and 5k can occupy the positions of NAD cofactor and the histone deacetylase inhibitor EX527 at the active site of SIRT1 enzyme.


Determination of antimicrobial activity of compounds 5a-r (agar disc-diffusion method)
Sterile filter paper discs (8 mm diameter) were moistened with compounds 5a-r solution in dimethyl sulphoxide of specific concentration (200 μg/disc), the broad-spectrum antibacterial drugs Ampicillin trihydrate, Ciprofloxacin and the antifungal drug Fluconazole (100 μg/disc) were carefully placed on the agar culture plates that had been previously inoculated separately with the microorganisms. The plates were incubated at 37 ºC, and the diameter of the growth inhibition zones were measured after 24 hours in case of bacteria and 48 hours in case of fungi.

Determination of minimal inhibitory concentrations (MIC) and the minimal biocidal
concentrations (MBC) for compounds 5a, 5c, 5g, 5l, 5m, 5o and 5q (micro-dilution susceptibility method) Compounds 5a, 5c, 5g, 5l, 5m, 5o and 5q, Ampicillin trihydrate, Ciprofloxacin and Fluconazole were dissolved in dimethylsulphoxide at concentration of 128 μg/mL. Two-fold dilutions of the solution were prepared (128, 64, 32, …, 0.5 μg/mL). The microorganism suspensions at 10 6 CFU/mL (colony forming unit/ml) concentrations were inoculated to the corresponding wells. The plates were incubated at 36 ºC for 24 and 48 hours for the bacteria and Candida albicans, respectively. The MIC values were determined as the lowest concentration that completely inhibited visible growth of the microorganism as detected by unaided eye. The MBC values were determined by the lowest concentration that killed of the microorganism by re-cultured on agar medium to verify the absence of growth.
The IC50 is the lowest concentrations of tested compounds that exhibited 50% inhibition on the biofilm formation.

Determination of in vitro anti-proliferative activity (MTT assay)
The tumor cells (3000 cells per well) were cultured and seeded into 96-well plates and the plates were incubated for 24 hours. The cells were then treated with compounds 5a-r and 1 Units PLAT978_ALERT_2_G Number C-C Bonds with Positive Residual Density.
5 Info 0 ALERT level B = A potentially serious problem, consider carefully 11 ALERT level C = Check. Ensure it is not caused by an omission or oversight 23 ALERT level G = General information/check it is not something unexpected 3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 21 ALERT type 2 Indicator that the structure model may be wrong or deficient 3 ALERT type 3 Indicator that the structure quality may be low 7 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check It is advisable to attempt to resolve as many as possible of the alerts in all categories. Often the minor alerts point to easily fixed oversights, errors and omissions in your CIF or refinement strategy, so attention to these fine details can be worthwhile. In order to resolve some of the more serious problems it may be necessary to carry out additional measurements or structure refinements. However, the purpose of your study may justify the reported deviations and the more serious of these should normally be commented upon in the discussion or experimental section of a paper or in the "special_details" fields of the CIF. checkCIF was carefully designed to identify outliers and unusual parameters, but every test has its limitations and alerts that are not important in a particular case may appear. Conversely, the absence of alerts does not guarantee there are no aspects of the results needing attention. It is up to the individual to critically assess their own results and, if necessary, seek expert advice.

Publication of your CIF in IUCr journals
A basic structural check has been run on your CIF. These basic checks will be run on all CIFs submitted for publication in IUCr journals (Acta Crystallographica, Journal of Applied Crystallography, Journal of Synchrotron Radiation); however, if you intend to submit to Acta Crystallographica Section C or E or IUCrData, you should make sure that full publication checks are run on the final version of your CIF prior to submission.

Publication of your CIF in other journals
Please refer to the Notes for Authors of the relevant journal for any special instructions relating to CIF submission.  (7) beta=99.633 (6) gamma=95.238 (6)  It is advisable to attempt to resolve as many as possible of the alerts in all categories. Often the minor alerts point to easily fixed oversights, errors and omissions in your CIF or refinement strategy, so attention to these fine details can be worthwhile. In order to resolve some of the more serious problems it may be necessary to carry out additional measurements or structure refinements. However, the purpose of your study may justify the reported deviations and the more serious of these should normally be commented upon in the discussion or experimental section of a paper or in the "special_details" fields of the CIF. checkCIF was carefully designed to identify outliers and unusual parameters, but every test has its limitations and alerts that are not important in a particular case may appear. Conversely, the absence of alerts does not guarantee there are no aspects of the results needing attention. It is up to the individual to critically assess their own results and, if necessary, seek expert advice.

Publication of your CIF in IUCr journals
A basic structural check has been run on your CIF. These basic checks will be run on all CIFs submitted for publication in IUCr journals (Acta Crystallographica, Journal of Applied Crystallography, Journal of Synchrotron Radiation); however, if you intend to submit to Acta Crystallographica Section C or E or IUCrData, you should make sure that full publication checks are run on the final version of your CIF prior to submission.

Publication of your CIF in other journals
Please refer to the Notes for Authors of the relevant journal for any special instructions relating to CIF submission.